Your comments

That shouldn't happen – maybe it's just a glitch. Did you try to restart the app and see if it works then?

(You have to press the home button to suspend the app, double-press the home button to bring up the list of recently used apps, hold your finger on the Textastic icon and tap on the red "minus" sign to quit the app – or just do a full restart of the iPad)

If that doesn't help: can you maybe post a video so I can try to reproduce the problem?
The menu appears when you either (slowly) tap two times at the same location or when you do a (quick) double tap somewhere in the text.

It also appears when you tap and hold to bring up the loupe and then release the finger from the screen.

This is more or less the standard behaviour on iOS.
Thanks for mailing the example file. I could reproduce the problem and will try to solve it for the next update.
I just tried this on my server and it works.

This might be a problem with a specific type of FTP server.

Which FTP server (product name, version number, running on which OS) are you connecting to? I appreciate any information that allows me to reproduce the problem. A demo account would be excellent.
While I could reproduce the problem with SVG files, the preview of the XHTML files I tried worked flawlessly. (I just tried this again)

Can you please send me an XHTML file that doesn't work for you to support*at*textasticapp.com or tell me a URL?
No problem. I'm glad it's working now :)
I just had a look at the source code, and the file changes are saved before the action sheet is displayed. You got me worried for a second :)

I don't know what happened there. If there were connection issues, you would have gotten an error message (if you didn't press the cancel button in the file transfer screen).

I just tried to reproduce the issue by adding a character to a file and immediately uploading it to my Dropbox, but it always worked...
I could add a third button to the alert: "Don't ask again" which would disable this message if you do a quick upload in the future.
That sounds like a really nice idea. Do you have any specific gestures in mind for some of those actions? (maybe two finger up for page up or something like that)